IRS1 and neoplasm: A. McGarry Houghton have demonstrated that NE induces degradation of insulin receptor substrate-1 (IRS-1) in tumor cell endosomes, as NE degraded IRS-1, there was increased interaction between phosphatidylinositol 3-kinase (PI3K) and the potent mitogen platelet-derived growth factor receptor (PDGFR), thereby skewing the PI3K axis toward tumor cell proliferation (118).